1. Field of the Invention
The present invention relates to an apparatus for posttreatment of exhaust gases of an internal combustion engine, using a reducing agent to be introduced into the exhaust gases, in particular a urea or a urea-and-water solution, having a mixing chamber, and to a mixing chamber.
2. Description of the Prior Art
Because of the ever-lower pollutant limits set in recent years, numerous apparatuses and methods for posttreatment of exhaust gases in internal combustion engines have been developed. For instance by means of catalytic converters systems that use urea and/or ammonia as a reducing agent for NOx conversion, efficient exhaust gas posttreatment systems have been made available.
To achieve a reduction in NOx components in exhaust gases, reduction catalytic converters have been developed, especially for Diesel engines, and these are typically divided into so-called SCR catalytic converters (for Selective Catalytic Reduction), with a urea metering system, and storage-type catalytic converters. The co-called SCR catalytic converters are regenerated by means of supplying a urea and/or ammonia reducing agent, while the so-called storage-type catalytic converters are regenerated, in so-called rich exhaust gas phases, with hydrocarbons from the engine fuel carried along with the exhaust gases.
From international patent disclosure WO 96/36797, a urea metering system with a compressed air delivery device for atomizing the urea is known, in which a check valve is provided in the compressed air path.
The object of the present invention is to improve an apparatus for posttreatment of exhaust gases in such a way that contamination of the air supply line, or of an on-board compressed air network communicating with it, can be reliably averted.